You must keep your bank records i.e. Bank statements, chequebooks and pay-in books as well as copies of Sales Invoices you have issued, receipts and delivery notes, invoices from your suppliers, and receipts for all cash transactions. If these are kept separated by month it will be easier for your Bookkeeper/Accountant at the year-end, thus saving you money.
If you are claiming ‘mileage’ you must keep a note of all mileage undertaken for business, this must include the date, details of the journey and number of miles. It is good practice to use a book kept in the vehicle for this purpose.
If you pay for things personally, you should make a note whether it is capital introduced or a loan to the business.
You must keep a record of goods and/or services taken from the business for personal use.
If you work from home you may be able to reclaim a proportion of your expenses for such things as telephone, internet costs, electricity & gas. You will probably have to reach agreement on this with your local HM Customs & Revenue Office.